 to tell if a cat is playing or fighting. Ears straight up mean the cat is playing, but the second they go horizontal, it's time to keep your distance. Cats invite playtime by assuming a submissive position. Aggressive cats will stand all fours and appear tense. Like many other animals, cats will try to make themselves look bigger when agitated. Flat fur is a good sign. Never get between two fighting cats. If things are getting a little too heated, clapping your hand should break the tension.